1. Field of the Invention
The present invention relates generally to receptacles for combustible materials, such as fuel tanks. More particularly, this invention relates to an improvement in the filler mass inserted in such tanks to prevent explosion. Specifically, this invention relates to the design of discreet filler elements which are used to fill a tank and which have folded in portions to prevent flaking of exposed end edges of layers of metal foil sheet material from which the filler mass is formed.
2. Description of the Prior Art
It is well known in the prior art that a filler mass insert for a tank may be formed from a metal foil mesh and will act to prevent explosion by transmitting heat from hot spots occurring on the tank exterior. This filler mass is traditionally formed of multiple layers of an expanded metal foil (U.S. Pat. No. 3,356,256), the method of manufacture thereof being well established in the art (U.S. Pat. No. 4,921,118). The resulting multi-layer mass can be either rolled into a coil, cut into pieces and stacked, or fan-folded (U.S. Pat. No. 4,149,649) to yield a filler mass of the size and shape of the cylindrical or rectangular tank to be fitted (U.S. Pat. No. 4,566,589).
More recently, various filler mass elements have been formed from foil material in order to retro-fit existing tanks and to accommodate tanks of irregular shape. These designs have not been entirely successful for a variety of reasons; but most importantly, because they all exhibit free edges which break off during use and then clog fuel lines (typically referred to as xe2x80x9cflakingxe2x80x9d). As an example, in U.S. Pat. No. 4,613,054 a spherical shaped filler element is disclosed. This filler element begins as a continuous sheet of mesh, is rolled into a cylinder, severed from the sheet, and finally crushed into a ball shape. It can readily be seen that this process creates a discreet, compacted filler element that, as a result of the construction process, will allow the mesh layers to xe2x80x9cnestxe2x80x9d and will leave exposed free edges on the exterior of the sphere. Moreover, the final crushing step compacts this filler element, reducing the available open interior space and thereby reducing its effectiveness as a filler mass. Similarly, in U.S. Pat. No. 5,000,336 another design for cylindrical and spherical discreet filler elements is presented. A strip of foil mesh having holes of irregular size is rolled into a cylindrical filler element and compressed into a sphere. By using holes of irregular size in the mesh, nesting of the mesh layers is reduced, but the problem of xe2x80x9cflakingxe2x80x9d from exposed edges is not resolved.
In U.S. Pat. No. 4,927,045 a different filler mass element is proposed which is described as having a long supporting member with a multitude of projecting plates. This element is used to retro-fit tanks with a filler mass by inserting the element through the tank opening; but the extensive number of free edges radiating from the supporting member in this design increases the xe2x80x9cflakingxe2x80x9d problem many fold, thereby preventing its use in any application where a clogged fuel line would pose an unacceptable risk.
Disclosures of previously proposed analogous and explosion proof containers are set forth in the following analogous and non-analogous U.S. Patents listed below.
It is a principal objective of this invention to provide a design for a discreet filler element which will eliminate the xe2x80x9cnestingxe2x80x9d and xe2x80x9cflakingxe2x80x9d problems inherent in the prior art.
It is a further objective to present such a design for a filler element which can be easily formed into a variety of shapes with minimal crushing to preserve the effectiveness of the filler mass.
The filler elements of the present invention are formed from a sheet of foil mesh material, or the like by a multiple fold technique. The folding process places the peripheral free edges of the sheet near the center of the filler element where the edges are protected and where any piece that should break off will be trapped.
For a rectangular sheet, the opposing sides are first folded inwardly along a crushed crease and then the opposing ends are similarly folded inwardly along a crushed crease. This creates an intermediate folded member which can then be rolled, molded, formed or folded again into a final desired shape for the filler element.
To eliminate nesting of the mesh within the filler element, various sections of the mesh corresponding to the folds are arranged to present openings of varying sizes, such that, when folded, sections of differing sized openings are juxtaposed.
According to the present invention there is provided a filler element for a tank comprising: a packet formed from at least one sheet of foil mesh, said at least one sheet of foil mesh being folded over several times such that peripheral free edges of the sheet of foil mesh are folded inwardly and are disposed internally of the packet thus formed.